The invention is related generally to the remote viewing of passageways and other limited access areas, and more particularly, to an apparatus having a sensor and light source for remotely viewing the condition of such limited access areas.
There has long been a need in the field of well boring to visually examine the bore hole for geological formations and for other conditions. In the operation and periodic maintenance of wells, it is frequently necessary to obtain information about the construction and operating condition of production equipment located downhole. Where these well bores have pipes and fittings, there is a continuing need to inspect this equipment for corrosion or other degradation. For example, detection of the onset of corrosion damage to well pipes within a bore hole enables the application of anti-corrosive treatments to the well. Early treatment of corrosive well conditions can prevent the highly expensive and dangerous replacement of corrosion damaged well production components.
Other maintenance operations in a production well environment, such as the replacement of various flow control valves or the inspection for the location and condition of casing perforations, make it highly desirable for an operator located at the surface to obtain accurate, realtime information about downhole conditions. A visible indication or record made to show precisely the location of any surface irregularities can greatly aid in maintenance.
One method of accomplishing this is to insert an instrument probe containing a camera, such as a closed circuit television camera, in the bore hole and move it through the area to be inspected. A compact, rugged instrument containing the camera and a light source is provided as the instrument probe. A cable is attached between the instrument probe and a surface station to communicate camera signals from the instrument probe to the surface station.
Such a logging instrument probe for well holes must be rugged to withstand the sometimes harsh conditions encountered in typical operation. For example, hydrostatic well pressures in excess of 4.2.times.10.sup.6 kilograms per square meter (6,000 pounds per square inch) and ambient well temperatures of 190.degree. C. (375.degree. F.) and above are not uncommon. Another common condition in bore holes is turbidity in the form of gases, mud, oil, and other fluids under high pressure. In many instrument probes, high intensity lighting such as that provided by quartz lamps or halogen lamps is provided to give bright light in the visible range for use with conventional television cameras.
In many cases, the size of the pipe in a well hole changes. For example, a length of pipe beginning at the surface may have a relatively small diameter but at some predetermined depth, the pipe's diameter may change or it may be connected to a pipe having a much larger diameter. Such a variable size passageway can cause a substantial inconvenience when using a logging instrument probe for inspection. In many cases, the light source of the instrument probe is located at a particular distance from the camera to accommodate a particular diameter of passageway. The distance between the camera and light source can be critical for a successful inspection, especially in conditions of turbidity.
The camera typically has a fixed field of view or angle of view and the size of the passageway determines the distance from the camera that the passageway is viewed. The light source must be of a type or configuration to illuminate the area of the passageway within the camera's view. Where the light source is positioned for illuminating one diameter passageway and the diameter of the passageway changes, the light source may not illuminate the section of the pipe which is now viewed by the camera. Due to turbidity and power source limits, the illumination of the subject matter is also limited. Even with very efficient electrical/light transducers, such as halogen bulbs, enough light may not be produced to cover all changes in passageway diameter.
In the case where the passageway under inspection includes sections of different diameter, the light source is usually positioned for inspection of one size of passageway and the inspection is then made. The instrument probe is then withdrawn from the well and the light source repositioned for inspection of the second size of passageway. Where a long passageway is to be inspected, a substantial amount of time can be involved in removing the probe from the well, repositioning the light source, and then reinserting the probe into the well. This can be a time consuming process and while the well is under inspection, it is usually unavailable for use. Thus, rapid inspection is desirable.
Hence, those skilled in the art have recognized that it would be desirable to provide an improved lighting system so that a well hole of different sizes can be inspected without having to remove the instrument probe to adjust the spacing of the light source from the camera for the particular diameter of the hole. Additionally, those concerned with instrument probes for use in viewing bore holes and casings have recognized the need for an improved light system which can be readily and easily assembled in the field after the size of the hole has been determined. Additionally, a light system which can be manufactured on
repeatable and economical bases would be desirable. The invention fulfills those needs.